For example, JP2009-96409A (which will be hereinafter referred to as Patent reference 1) discloses a known electric tilt steering apparatus at which an output shaft of an electric motor and a tilt screw shaft are arranged to be parallel with each other. The output shaft of the electric motor and the tilt screw shaft are connected to each other via a speed reduction device. As the speed reduction device, a worm and a worm wheel are used. In an embodiment of Patent reference 1, it is described that a worm and a worm wheel, which serve as a motor speed reduction device and which are not shown, are accommodated inside a motor case. It is also described in Patent reference 1 that a movable nut member is screw-joined to a tilt screw in a state where the tilt screw is put into or screwed into the movable nut member, and a lower portion of a swing arm is connected to the movable nut member via a link mechanism (which are described in paragraphs [0028] and [0029] of Patent reference 1, however, figure numbers and reference numerals are omitted).
Further, it is described in Patent reference 1 that the other end of a telescopic screw is rotatably supported by a lower surface of an upper jacket via a bracket that will be described below, and that a motor is connected to the other end of the telescopic screw via a worm and a worm wheel which are not shown (which is described in paragraph [0032] of Patent reference 1, however, figure numbers and reference numerals are omitted). Thus, the known steering apparatus also includes a telescopic mechanism at which an output shaft of the motor and a telescopic screw shaft are arranged to be parallel with each other. The worm and the worm wheel are used as the speed reduction device of the output shaft and the telescopic screw shaft.
Generally, at a steering apparatus including an electric telescopic mechanism and/or an electric tilt mechanism, a threaded shaft provided with trapezoidal screw threads is used as the tilt screw shaft and/or the telescopic screw shaft which are described above. Generally, a worm speed reduction mechanism such as the speed reduction device described in Patent reference 1 is used as a speed reduction device of an electric motor output to the threaded shaft. In the worm speed reduction mechanism, a space portion is needed for the electric motor to be arranged in a direction perpendicular to the threaded shaft and the electric motor is arranged in a manner that the electric motor projects from a steering column. Accordingly, not only the entire apparatus inevitably increases in size but also it may be difficult for the apparatus to be mounted on a vehicle. On the other hand, as illustrated in FIGS. 8 and 9, according to some known apparatus, the output shaft of the electric motor is arranged to be parallel with the threaded shaft by interposing, for example, a spur gear between the threaded shaft and the worm speed reduction mechanism. However, the increment in size of the entire apparatus is inevitable, and the number of parts and components increases, thereby contributing to cost increment.
As described above, on the premise that the output shaft of the electric motor includes either a relationship of orthogonality or a relationship of parallelism relative to the threaded shaft, the electric telescopic mechanism and/or the electric tilt mechanism are not only required to be small in size and be light, but also required to be easily arranged. In such a circumstance, a further reduction in size and space-saving are enabled by a configuration in which the threaded shaft and the output shaft of the electric motor are connectable to each other with any of the relationship of parallelism, a relationship of inclination where an angle is provided between both of the shafts (accordingly, including the orthogonality) and a relationship of skew where the both shafts do not intersect each other.
A need thus exists for a steering apparatus for a vehicle, which is not susceptible to the drawbacks mentioned above.